Method for producing fourth group metals



I mambn FOR-PRODUCING FOURTH GROUP METALS Elsi 09? 26,1954

INVENTOR ROBERT M. M KINNEY 4 ATTORNEY METHOD FOR PRODUCING FOURTH GROUP METALS Robert Myers McKinney, Wilmington, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington,

Del., a corporation of Delaware Application October 26, 1954, Serial No. 464,88 2

' 10 Claims. 01. 7s s4.s

This-invention relates to an improved method for the production of fourth group metals such as titanium,

zirconium and hafnium by the chemical reaction of tetrachloride of the fourth group metal and a metal reducing agent.

Titanium metal is currently produced in commercial quantities by the reduction of titanium tetrachloride with 2 ,839,384 Patented June 17, 1958 Ice method for producing the metal product'in dense form- .and free of occluded by-product salt. A still further object is the production of titanium in a form that is easily removable from the reaction vessel. Further objects include the production of titanium of low surface area, high ductility and freedom from unreacted reagents such as lower chlorides of titanium and unconverted reducing metal.

The above and other objects are attained by my improved process which comprises injecting a stream of titanium tetrachloride into a reaction vessel containing 1 ,a vaporous metal reducing agent and toward a titanium metal targetextending into the zone of reaction within said =reaction vessel while simultaneously maintaining the supply of the reducing agent within the vessel by addition of the reducing metal thereto. These conditions 7 require the maintenance of a temperature within the magnesium. The Kroll process as revealed in U; S.

Patent 2,205,854 is well known in the industry and provides a batch method for the interaction of vaporous titanium tetrachloride and liquid magnesium within a metal chamber-and in the presence of a noble gas such as helium or argon. The product resulting from this process is in sponge form, has a high specific surface area, and upon draining of the by-product magnesium chloride salt from the reaction vessel, retains substantial amounts of unreacted magnesium and magnesium chloride within its porous structure. The metal product must be mechanically removed from the reaction vessel since the sponge body adheres strongly to the interior metal surface of the container. The salt and the unreacted metalreducing agent must be separated from the sponge titanium and vacuum distillation has been proposed to free the sponge of these contaminants and'provide titanium of high purity. An alternative method of first removing the product from the reaction vessel and aqueous leaching the same in the presence of an acid has been referred to in the patent and general literature in this field. This prior art reduction method has not been converted to continuous operation due to the fact that the sponge adheres to the reaction chamber and requires batch methods for its removal. The use of a boring'ma chine technique for separation of the sponge from the container requires a cooling-down of the material prior to its removal so as to avoid contamination and the method is cumbersome as well as time-consuming. The use of disposable liners for the reaction vessel has also been proposed and this innovation permits the removal of the batch from the reaction vessel, the stripping of the (bin metal container from the adhering sponge and a Shorter cycle in the process by an earlier return of the reaction vessel to the production of sponge.

Efforts have been made to provide continuous methods 4.,- the production of titanium sponge in a manner that Anon-adhering sponge product is produced and may be removed from the container. These products like the Kroll product are also easily contaminated by contact with the atmosphere due to their high specific surface area.

The substitute continuous processes have been carried out in small scale equipment but their attractiveness as a substitute for the batch method has not, as yet, been demonstrated.

It is an object of the present invention to overcome the shortcomings of the prior art methods and provide a method for the preparation of fourth group metals, e. g., titanium, in a direct and simple manner from the tetrachloride and a reducing metal. A' further-object i stoward the titanium metal target.

reaction vessel sufficiently high to permit the existence of'the reducing metal in the vaporous condition, such an atmosphere being a requirement of the method.

My improved process, when employed in the production'of titanium metal requires the injection of titanium tetrachloride into a vessel having present therein a gaseous reducing agent suitably selected from the group consisting .of alkali and alkaline earth metals having utility in the prior art processes and also providing within this reaction chamber a titanium metal target on which the reaction between the two ingredients takes place. The

reaction between vaporous titanium tetrachloride and gaseous reducing agent such as sodium, potassium, magnesium and the other alkaline earth and alkali metals does not readily take place unless a solid surface is pro vided. The titanium metal target within the reactionv vessel provides the surface, and accordingly, the best operating conditions prevail when the titanium tetrachlorideis added in a vaporous condition and in a stream directed agent may be added to the reaction chamber as a solid,. as a liquid or in the vaporous condition depending upon. wishes of the operator. Its addition as a liquid is attrac-- tive and the heat of reaction between the titanium tetra chloride and the reducing agent is quite sufficient to va-- porize the more common members of the alkali metal-i group, namely sodium and potassium. It is understood that other elements of the alkali metal group such as lithium, rubidium and cesium might be used by the selection of reaction conditions as outlined herein, but no substantial advantages over sodium found.

The process as outlined above and in a preferred embodiment thereof may be conveniently carried out in an apparatus of the type shown in the accompanying drawing. This can comprise a reaction vessel 1 for confining the vaporous reducing metal above a body of the molten by-product salt 2 within a tank 3 as produced in the reaction. The vessel 1 may be bell-shaped with the and potassium have been open bottom of the bell extending downwardly into a bath of molten chloride of the reducing metal. Such an inverted reaction vessel must have inlet means for the addition of the reagents and the titanium tetrachloride stream is convenientlyadded through an inlet 4 at the top with a direction downwardly toward the center of the vessel. The reducing metal e. g. sodium or potassium may be passed as a liquid upwardly through a pipe 5 to the surface 6 of the molten alkali metal salt where it will evaporate from the hot surface and feed the reagent in vaporous form into the reaction zone 7 enclosed by the vessel. The latter may be constructed of iron and jacketed for cooling. The titanium metal target 12 on which the reaction-product '8 builds may suitably extend upward The metal reducing.

through the molten salt and into theinterior of the inverted reaction chamber.

The inverted. reaction vessel may be of simple design, e. g. hemispheroidal and be constructed of iron or any other suitable metal. Upon cooling this reaction vessel,

the alkali metal chloride vapors generated by the reaction will condense on the interior surface to form a solid 'salt layer and this layer will grow until equilibrium conditions prevail wherein the temperature of the interior surface of the salt layer will be at the melting point of the salt. In reality one conducts the reaction within an alkali metal chloride container and out of contact with all metals other than the metal being consumed and the metal being pro-, duced. The temperature in the zone of reaction and on the surface of the metal target may' substantially exceed the boiling point of the alkali metal chloride being produced, i. e., 1407" C. for potassium chloride and 1465" C for sodium chloride. The exposed surface of the container will have a temperature equal to the melting point of the by-product salt, namely 706 C. for potassium chloride and 800 C. for sodium chloride. The temperature of'the liquid salt at the base of the reaction vessel can be varied by use of cooling coils or other means to withdraw heat therefrom so as to dissipate the heat of reaction generatedreactant in the vapor state, the temperature within said zone being in excess of the dew point of the chloride byproduct salt while the solid internal salt surface confining the vaporous metal reactant is maintained at the melting point of the said salt. The high temperature of the metal target surface within the reaction zone results from the heat of reaction between the reducing metal and the tetrachloride. Heat is dissipated from this surface by radiation and by movement of the hot salt vapors toward the cooler surfaces where condensation to liquid salt takes place. The rate of addition of the tetrachloride determines the rate of reaction and the resultant rate of heat generation as well as the production capacity of the apparatus. Proximity of the target metal surface to the cooler surfaces also plays a role in the loss of heat from the reaction zone.

Sodium and potassium are thepreferred reducing metals for use in my invention when practised in the feet in diameter and three feet in length and welded to a hemispherical section 10 having an equal radius was used as the reaction chamber. This was inverted (dome top and open bottom) and the opening submerged in a tank of molten potassium chloride. The jacketing was divided into four sections 11, one for the hemispherical portion, and three sections of equal height on the tubular portion of the apparatus which extends into the molten salt. An inlet pipe 4 at the top of the dome was used for the admission of a jetted stream of TiCl vapors downward toward a mound of titanium metal 8 supported on a platform 12 and extending upward from the molten salt surface 6, the support being from below with means 15 for adjustment of height. Liquid potassium was released from a pipe 5 extending into molten salt and under the dome shaped chamber 1. A conduit 14 for the admission and withdrawal of argon and reducing metal vapors from the reaction vessel was also provided so that substantially atmospheric pressure within the vessel prevailed at all times and particularly if the supply of reducing metal should inadvertently fall below its rate of consumption.

previously established and maintained by addition of a excessive temperature.

salt was etfectively cooled by the flow of condensed salt manner just described. Optimum operating conditions prevail when a substantial part of the atmosphere within the salt-lined vessel is the vaporized reducing metal, the accompanying gases being an inert material such as argon or helium. The conditions as outlined require a metal having an appreciable vapor pressure at the melting point of its chloride and the selection of sodium and potassium follows when we look at the pertinent data for these elements. The vapor pressure for the metallic element at the melting point of chloride is 275 mm. for sodium, 755 mm. for potassium, 6 mm. for magnesium and even lower values for lithium, calcium, strontium and barium than for magnesium. Cesium and rubidium compare favorably with sodium and potassium in vapor pressure properties but until they are commercially available, one must prefer sodium and potassium. These four alkali metals, in common, have vapor pressure values above 200 mm. at the melting point of their respective chlorides. For this reason they are recommended for use in the embodiment of my invention wherein there is exposed a solid by-product salt layer at its melting point.

The following specific examples are given as illustrative of the invention and are not to be regarded as limiting the invention.

Example I panying'drawing consisting of a tubular section 9 three potassium stream which rises .through the liquid potassium chloride and from the surface of which it passes as a gas. Argon was supplied to the react-ion vessel through the mentioned pipe connection in an amount sutficient to maintain atmospheric pressure within the vessel. Gases were also allowed to escape from the chamber when the desired pressure was exceeded for any reason.

The two reactants were admitted to the vessel at equivalent rates and care was taken to insure a reducing atmosphere with similar care taken to avoid excessive evaporation of the reducing metals on the surface of the molten salt and its condensation on the solid salt surface where the temperature is lower. Water was passed through the jacket of the vessel so as to maintain a salt skull 15 on the inside surface extending above the molten salt but no coolant fiuid was passed through the jacket chambers that were immersed in the salt unless the latter reached an It was found that the molten from the skull surface and by the evaporation of potassium from the surface. The temperature within the reactor was followed by shielded thermocouples extending within the gas filled portion of the vessel and into the surface of the molten salt. The gaseous TiCl was added as rapidly as it was consumed by the reaction at the hot metal surface which was maintained high enough to evaporate the salt formed in the reaction and this resulted in a deposit of dense titanium of low specific surface with a feathery appearance. As the deposit grew in height, the platform support was lowered so as to maintain a substantiall constant distance from the inlet for the TiCl, to the metal surface within the reaction zone.

During the reaction an effort was made to maintain at atmosphere comprising at least 90% potassium vapor with the remaining amount being argon and at atmosphenc pressure. The solid salt surface temperature automatically adjusted itself to 770 C. and the rate of feeding of the reactants was such that the rate of heat generation maintained a metal target temperature about or slightly above the dew point of potassium chloride so as to insure its vaporization from the metal surface. This temperature wast-effected by control of (1) the rates of reaction (2) the closeness of the target surface to the salt surfaces and (3) the temperature of the molten salt pool. These were adjusted to give maximum temperature until the target reached the. boiling temperature of potassium chloride when adjustments were made to prevent a further temof the adhering salt by an aqueous washing.

Example 11 The operation of Example I was repeated using the same apparatus, but the substitution of sodium as the reducing metal and sodium chloride for the salt bath. 1 The TiCl was added in exactly the same way as previously, but the sodium was added as a vaporous stream upward through the molten salt bath with care being taken to provide 30-35% sodium by volume in the atmosphere within the reaction vessel. The temperature of the salt skull adjusted itself to 800 C., the melting point of sodium chloride, and the salt bath was maintained in excess of the melting point.

The product resembled the product of Example I in every way. 1

The above examples are specific to the production of titanium metal in dense form and in a manner such that the product can be readily removed from the reactor without having to cool the reactor prior to removal of the metal from the vessel as has been characteristic of prior art methods. The process is equally applicable to the production of other group IV B metals, i. e. zirconium and hafnium by substitution of zirconium tetrachloride or hafnium tetrachloride as the reactant in place of titanium tetrachloride. The operating conditions are largely dictated by the properties of the reductant and the by-product chloride salt and accordingly, the same precautions and operating conditions prevail when substituting zirconium or hafnium chloride for titanium chloride in carrying out the invention as detailed in Examples I and H.

Potassium boils only 9 C. higher than the melting point of its chloride and accordingly, one can readily operate with a 100% potassium atmosphere with the reaction vessel. Sodium on the other hand has only about 275 millimeters vapor pressure at themelting point of sodium chloride and this requires the use ofan inertgas such as argon or helium to maintain atmospheric pressure conditions within the vessel.

While the reducing metal was allowed to enter the reaction zone by upward movement through the molten salt in the above examples, it is obvious that the reducing metal may be added as a liquid or a gas from above and through an opening in the vessel itself. A jet similar to the jet for the admission of titanium tetrachloride is considered within the scope of the invention; v

The examples disclose the use of sodium and potassium which are the preferred reducing metals due to the fact that they are the commercially available members of the alkali metal group having a boiling point of less than 1000 C. and having a chloride which boils at less than 1500* C., these being desirable operating temperatures. Potassium permits the operation to be carried out at lower temperatures than does sodium and has a further advantage over sodium of permitting the process to be carried out at substantially atmospheric pressure in the absence of substantial amounts of an inert gas. However, sodium has an economic advantage for commercial operation and these outweigh the technical advantage of potassium as the reducing metal in the process as disclosed. Both reducing metals are considered commercially attractive.

I claim as my invention:

1. A method for the production of a metal selected from the group consisting of titanium, zirconium and jhafnium in solid form and free of occluded by-product salt by reaction of the tetrachloride of said metal with a reducing metal selected from the group consisting of alkali and alkaline earth metals which comprises injecting a stream of the tetrachloride into a reaction vessel containing vapors of said reducing metal and above a pool toward a solid target surface of a supported, movable body of the solid metal being produced which extends above the surface of said pool and into the zone of reaction within said reaction vessel and during the reduction is. maintained within the reaction zone at a substantially constant distance from the point of said tetrachloride injection, maintaining all surfaces of said target exposed to the said vapors within the said vessel at a temperature not lower than the melting point of the chloride salt being produced, cooling the interior surfaces of taining the supply of reducing metal within the vessel by adding it at substantially its rate of consumption, and withdrawing said target and solid metal product from said vessel through said pool to recover said product.

2. A method for the production of a metal selected :from the group consisting of titanium, zirconium and hafnium, in solid form and free of occluded by-product salt-by reaction of the tetrachloride of the metal with a reducing alkali metal which comprises injecting a gaseous stream of the tetrachloride into a reaction vessel containing vapors of said reducing metal above a pool body of molten by-product alkali metal chloride which seals the bottom of said vessel, charging said stream toward a solid target surface of a supported, movable body of the solid metal being produced which extends above the surface of said pool body and into the zone of reaction within Within said vessel at a temperature at least equal tothe melting point of the chloride salt being produced, cooling the interior surfaces of said vessel to maintain thereover a solid coating of alkali chloride by-product, simultaneously maintaining the partial pressure of the reducing metal within the vessel in excess of about 200 millimeters by adding said reducing metal thereto at substantially its rate of consumption and withdrawing said target and solid metal product from said vessel through said pool to recover said product.

3. A method for the production of titanium metal in solid form and free of occluded by-product salt by reaction of titanium tetrachloride and a reducing alkali metal having a partial pressure of at least 2G0 mm. at the melting point of its chloride which comprises maintaining vapors of said reducing metal within an inverted reaction vessel sealed at its bottom by contact with a pool of molten alkali metal chloride, injecting a gaseous stream of said tetrachloride reactant into the reaction zone of said vessel toward a solid target surface of a supported, movable body of the titanium metal being produced which extends above the surface of said pool body into saidreaction zone and during the reaction is maintained within said zone at a substantially constant distance from the point of said tetrachloride injection with its surface temperature being in excess of the dew point of by-product alkali metal chloride salt formed, maintaining the internal surface of the reaction vessel at a temperature below the melting point of said alkali metal chloride to form said chloride as a solid coating thereover, replenishing the supply of said reducing metal within the reaction zone by adding it at substantially its rate of consumption in the reaction, and recovering the titanium metal product by withdrawing said target and titanium metal product from said vessel through said pool.

4. A method for the production of titanium metal in solid form and free of occluded by-product salt by the reduction of titanium tetrachloride with sodium which comprises injecting a gaseous stream of titanium tetrachloride downwardly through the top of a bell-like reaction vessed into a reaction zone thereof and a confined atmosphere of gaseous sodium onto a solid target surface of a supported, movable body of said solid titanium metal which projects upwardly into said reaction zone and above a pool body of molten sodium chloride maintained at the bottom of said reaction'vessed, sealing the bottom portion of said vessel by submerging the same in said pool of molten sodium chloride, cooling the in ternal surfaces of said vessel to form and maintain a coating of solid sodium chloride thereover, during the reduction maintaining said target surface in said reaction zone at a substantially constant distance from the point of said tetrachloride injection and at a temperature in excess of the dew point of the sodium chloride byproduct formed, feeding sodium to said vessel at substantially its rate of consumption in theproduction of the titanium metal on the surface of said target surface and while maintaining an excess of sodium within the vessel during the reaction, and recovering the titanium metal so produced by withdrawing said target and metal from said vessel through said pool. i

5. A method for the production of titanium metal in solid form and free of occluded by-product salt; by the reduction of titanium tetrachloride by potassiumlwhich comprises injecting a gaseous stream of titanium tetrachloride downwardly through the top of a bell-like .reaction vessel into a reaction zone thereof and a confined atmosphere of gaseous potassium onto a solid target surface of a supported, movable body of said solid titanium metal which projects upwardly into said reaction zone and above a pool body of molten potassium chloride maintained at the bottom of said reaction vessel and in which said vessel bottom is submerged to effect a seal therefor, during the reduction maintaining said target surface in said reaction zone at a substantially constant distance from the point of said tetrachloride injection and the temperature thereof in excess of the dew point of the potassium chloride by-product formed, cooling the internal surfaces of said vessel to form and maintain a coating of solid potassium chloride thereover, feeding potassium to said vessel at substantially its rate of consumption in the production of titanium metal on said target surface and while maintaining an excess of potas-' containing an atmosphere of vaporized sodium as a reductant metal, externally cooling said vessel to below the melting point of sodium chloride and to provide a solid coating of sodium chloride over said internal surfaces, sealing the bottom portion of said vessel by submerging said portion in a pool of molten alkali metal chloride above the surface of which pool said target projects, during the reduction reaction maintaining said target surface in said reaction zone at a substantially a covering the titanium product by withdrawing said targe from the reaction vessel through said pool.

7. A method for the production of titanium metal insolid'form and free of occluded by-product salt which comprises injecting a stream of vaporous titanium tetrachloride downwardly onto a solid target surface of the supported, movable titanium metal product projecting upwardly within a closed reaction zone of an inverted reaction vessel maintained atatmospheric pressure and containing an atmosphere of vaporized potassium as a rcductant metal, externally cooling said vessel to maintain its internal surfaces below the melting point of potassium chloride and provide a solid coating of potassium chloride over said internal surfaces, sealing the bottom portion of said vessel by submerging it in a pool ofmolten alkali metal chloride above the surface of which pool said target projects, during the reductionreaction maintaining said target surface in said reaction zone at a substantially constant distance from the point of said titanium tetrachloride injection and at a temperature in excess of the dew point of the potassium chloride formed, maintaining said potassium atmosphere by feeding potassium into said vessel at substantially its rate of consumption in reaction with said titanium tetrachloride, and recovering the titanium product by withdrawing said target from the reaction vessel through said 001. P 8. A method for the production of titanium metal in solid form and free of occluded by-product salt which comprises injecting a stream of vaporous titanium tetrachloride downwardly onto a solid target surface of a supported, movable titanium metal product projecting upwardly within a closed reaction zone maintained under atmospheric pressure in an inverted bell-like reaction vessel containing vapors of an alkali metal reductant having a vapor pressure of at least 200 millimeters at the melting point of its chloride salt, cooling said vessel to maintain its internal surfaces below the melting point of a chloride of said reductant and to provide thereover a coating of a solid chloride salt of said alkali metal, sealing the bottom portion of said vessel by submerging said portion in a pool of an alkali metal salt having a temperature at least equal to its melting point and above the surface of which pool said target projects, during the reduction reaction maintaining said target surface in said reaction zone at a substantially constant distance from the point of said titanium tetrachloride injection and at the temeprature in excess of the dew point of the alkali metal chloride formed, maintaining an atmosphere of said reductant in said reaction zone by feeding the alkali metal into the reaction vessel substantially at the rate of its consumption through interaction with titanium tetrachloride, and recovering the titanium metal product by withdrawing said target from the reaction vessel through said pool.

9. A method for the production of titanium metal in solid form and free of occluded by-product salt which comprises injecting a stream of vaporous titanium tetrachloride downwardly onto a solid target surface of a supported, movable titanium metal project projecting upwardly within a closed reaction zone maintained under atmospheric pressure in an inverted bell-like reaction vessel containing vapors of sodium and cooling said vessel to maintain its internal surfaces below the melting point of sodium chloride to coat said internal surfaces with solid sodium chloride, sealing the bottom portion of said vessel by submerging said portion in a pool of molten sodium chloride having a temperature at least equal to its melting point and above the surface of which pool said target projects, during the reduction reaction maintaining said target surface in said reaction zone at a substantially constant'distancc from the point of said ,titaniurn tetrachloride injection and at a temperature in excess of the dew point of the sodium chloride formed,

maintaining said sodium vapors in said reaction zone by feeding sodium thereto at substantially its rate of consumption through interaction with titanium tetrachloride, and recovering the titanium metal product by withdrawing said target from the reaction vessel through said pool.

10. A method for the production of titanium metal in solid form and free of occluded by-product salt which comprises injecting a stream of vaporous titanium tetrachloride downwardly onto a solid target surface of a supported, movable titanium metal product projecting upwardly within a closed reaction zone maintained under atmospheric pressure in an inverter bell-like reaction vessel containing vapors of potassium and cooling the internal surfaces of said vessel to coat said surfaces with solid potassium chloride, sealing the bottom portion of said vessel by submerging said portion in a pool of molten potassium chloride having a temperature at least equal to its melting point and above the surface of which pool said target projects, during the reduction reaction maintaining said target surface in said reaction zone at a substantially constant distance from the point of said titanium tetrachloride injection and at a temperature in excess of the dew point of the potassium chloride formed, maintaining the potassium vapors in said reaction zone by feeding potassium thereto substantially at its rate of 10 consumption through interaction with titanium tetrachloride, and recovering the titanium metal product by withdrawing said target from the reaction vessel through said pool.

References Cited in the file of this patent UNITED STATES PATENTS 1,306,568 Weintraub June 10, 1919 2,091,087 Wempe Aug. 24, 1937 2,148,345 Freudenberg Feb. 21, 1938 2,205,854 Kroll June 25, 1940 2,270,502 Bucher Jan. 20, 1942 2,586,134 Winter Feb. 19, 1952 2,607,674 Winter Aug. 19, 1952 2,621,121 Winter Dec. 9, 1952 2,647,826 Jordan Aug. 4, 1953 2,708,158 Smith May 10, 1955 2,760,858 Findlay et a1. Aug. 28, 1956 2,763,542 Winter Sept. 18, 1956 FOREIGN PATENTS 1,088,006 France Sept. 1, 1954 827,315 France Jan. 24, 1938 296,867 Germany Mar. 13, 1917 505,801 Belgium Sept. 29, 1951 

1. A METHOD FOR THE PRODUCTION OF A METAL SELECTED FROM THE GROUP CONSISTING OF TITANIUM, ZIRCONIUM AND HAFNIUM IN SOLID FROM AND FREE OF OCLUDED BY-PRODUCT SALT BY REACTION OF THE TETRACHLORIDE OF SAID METAL WITH A REDUCING METAL SELECTED FROM THE GROUP CONSISTING OF ALKALI AND ALKALINE EARTH METALS WHICH COMPRISES INJECTING A STREAM OF THE TETRACHLORIDE INTO A REACTION VESSEL CONTAINING VAPORS OF SAID REDUCING METAL AND ABOVE A POOL BODY OF MOLTEN BY-PRODUCT REDUCING METAL CHLORIDE WHICH SEALS THE BOTTOM OF SAID VASSEL, CHARGING SAID STREAM TOWARD A SOLID TARGET SURFACE OF A SUPPORTED, MOVABLE BODY OF THE SOLID METAL BEING PRODUCED WITH EXTENDS ABOVE THE SURFACE OF SAID POOL AND INTO THE ZONE OF REACTION WITHIN SAID REACTION VESSEL AND DURING THE REDUCTION IS MAINTAINED WITHIN THE REACTION ZONE AT A SUBSTANTIALLY CONSTANT DISTANCE FROM THE POINT OF SAID TETRACHLORIDE INJECTION, MAINTAINING ALL SURFACES OF SAID TARGET EXPOSED TO THE SAID VAPORS WITHIN THE SAID VESSEL AT A TEMPERATURE NOT LOWER THAN THE MELTING POINT OF THE CHLORIDE SALT BEING PRODUCED, COOLING THE INTERIOR SURFACES OF SAID VESSEL TO MAINTAIN THEREOVER A SOLID COATING OF REDUCING METAL CHLORIDE BY-PRODUCT, SIMULTANEOUSLY MAINTAINING THE SUPPLY OF REDUCING METAL WITHIN THE VESSEL BY ADDING IT AT SUBSTANTIALLT ITS RATE OF CONSUMPTION, AND WITHDRAWING SAID TARGET AND A SOLID METAL PRODUCT FROM SAID VESSEL THROUGHT SAID POOL TO RECOVER SAID PRODUCT. 